Obesity is associated with insulin resistance, characterized by increased circulating insulin levels and peripheral resistance to the effects of insulin. The risk of developing diabetes mellitus is increased significantly in the obese. The magnitude of this risk increases with the degree and duration of obesity, but overall the relative risk is about 3. Approximately 90% of diabetes mellitus is type 2, or adult onset diabetes, and 90% of type 2 diabetics are overweight. Improved glycemic control is directly related to weight loss in type 2 diabetes mellitus. Even modest amounts of weight loss can improve glucose control. Short-term weight loss can often be achieved by any of a variety of methods. However, long-term results from weight loss programs have been disappointing in nondiabetics as well as diabetics. At one year the mean weight regain, regardless of the program is from 40-60%, and by 4-5 years most patients have regained 95% of the weight they originally lost. Without adequate maintenance of wight loss, glucose control is unlikely to improve long-term. Energy restriction, separate from weight loss, will also improve glucose control, but unless this is sustained over a period of time and leads to weight loss the improvement will be temporary. Over $30 billion dollars is spent each year in the US on diet and diet aids. Yet there is little data on weight loss and glucose control using commercial products. This proposal seeks to evaluate two commercial liquid dietary meal replacements as to their effect on weight, glucose control, and other metabolic indices both short and long-term in a randomized, prospective study.